Although much is known about the structure and function of membranous organelles, few of the molecular details of their assembly are presently understood. It is the objective of the proposed research to examine the formation of the bacterial photosynthetic apparatus as a simple and experimentally accessible model system for the formation of organelle membranes. Bacterial strains have been chosen in which the morphogenesis of the photosynthetic apparatus can be induced in cells devoid of this structure. The sequence in which various electron transport intermediates and pigment components are assembled during induction of membrane formation will be determined. To further examine the role of the peripheral membrane in the formation of the photosynthetic apparatus, highly purified membrane preparations will be thoroughly characterized. The possibility that the peripheral cytoplasmic membrane contains precursors of the photosynthetic membrane will be critically examined in labelling studies. Other labelling experiments will test whether levels of membrane lipid and protein components can be independently varied. If membrane composition can be altered in this manner, density-shift experiments will be conducted with phospholipid-precursor-requiring mutants. The proposed studies will aid in elucidating the mechanism of organelle assembly and will provide a more complete understanding of this process at the molecular level.